New advances in material science provide engineers with various options while designing. Thanks to the available production technologies, scientists can combine elements to create composites, alloys, and compounds with superior performance statistics.
Magnesium and its alloys are a great example of what modern-day material science can accomplish. Magnesium is the lightest structural metal however, the brittle and flammable nature of the element disallows engineers to use it without combining it with other materials.
When combined with other materials, the lightweight nature of Magnesium pushes it forward. Industries such as aerospace and automotive utilize magnesium alloys frequently.
However, the longevity of the material is crucial for structural integrity, especially for mentioned industries. The biggest threat to longevity is corrosion. In this article, we’ll talk about the types of magnesium alloys, their characteristics, how magnesium alloys corrode, and how to prevent corrosion.
Common Magnesium Alloys
Magnesium is usually paired with elements that will improve its brittle nature. Some of the most common elements that are alloyed with magnesium are aluminum, zirconium, zinc, manganese, silicon, and copper. In addition to the desired characteristics, partner elements are also chosen per the preferred method of production.
Characteristics Of Magnesium Alloys
Magnesium alloys have a hexagonal structure, which means low specific gravity with great strength. For comparison, magnesium has a density of 1800 kg/m3 while aluminum’s density is 2400 kg/m3. When combined with other elements, magnesium has better physical strength than aluminum alloys. To summarize, magnesium is lighter and stronger than aluminum making it a great choice for the aerospace and automotive industries.
In addition, magnesium performs well under high temperatures as well. Resistance to creep deformation plays a big role in the aerospace industry, making magnesium alloys a great choice. Magnesium on its own has very poor creep resistance but studies show when combined with other elements, the creep resistance can be increased up to 600%.
Corrosion resistance is another important property of various industries. Where magnesium in its pure form has already great corrosion resistance, magnesium alloys perform perfectly in this regard. There are preventative measures available to increase corrosion resistance but to apply the correct measure, how magnesium alloys corrode must be studied first.
How Do Magnesium Alloys Corrode?
Various factors in play trigger corrosion in magnesium alloys. Two main categories that affect corrosion directly can be listed the metallurgy of the alloy and environmental factors.
Magnesium alloys are generally made up of two main alloying elements; aluminum and zirconium. Alloying elements have a great influence on the alloy’s corrosion resistance. In general, aluminum-alloyed magnesium has greater corrosion resistance compared to other alloying elements.
Another metallurgy bases factor that affects corrosion is impurity elements. The alloying process is never perfect. Chemical reactions are almost impossible to perform perfectly as suggested by the chemistry equations. Elements mixed in the atmosphere, various contaminants, and heat play a huge part in forming impurities. In most cases, small quantities of unwanted elements and compounds form in the alloy. These impurities can be thought of as a weak spots since they are less resistant to corrosive effects and they decrease the overall physio-chemical performance of the alloy.
In terms of environmental factors that affect corrosion, atmosphere and solutions are the two most commonly encountered reasons. Atmospheric effects on magnesium are usually superficial, meaning the corrosion layer does not penetrate the material. Studies show that once the layer of oxidation is formed on the surface of the material, alloying contents disallow the corrosion to continue into the material. This makes protecting the surface of magnesium alloys so important.
Solutions, on the other hand, are a weak point of magnesium alloys. Material scientists studied the influence of various acidic solutions on magnesium alloys and the findings were as expected. As per most metals and alloys, magnesium-based alloys perform poorly under low pH conditions, acid diffuses the chemical and physical bonds between alloying elements and corrosion occurs.
As mentioned earlier, magnesium is a structural metal with low specific density, meaning that its lighter than most metals and alloys. We’ve also mentioned that this property makes it a great choice for the automotive industry. Magnesium alloys are used in various parts of an automobile but the most common area of use is the engine block. The low specific density of the magnesium alloys for the lighter engine block.
However, this area of use brings a specific problem with it; magnesium alloys’ interaction with coolants.
Studies show that magnesium alloys are quite resistant to corrosion through coolant. However, if the alloy is intended to be used in the engine block, it is suggested that the alloy’s main element should be Zirconium since it provides the alloys with greater corrosion resistance under the specified conditions.
Thanks to new production technologies, engineers and designers have access to a more versatile range of materials. Magnesium and its alloys have proven to be a great choice for automotive and the aerospace industries. Due to the expected lifetime of automobiles and aircraft, the longevity of the structural materials is crucial. To take preventative measures against corrosion, a better understanding of how magnesium alloys corrode is required.